Previous studies indicated that Treg suppressed colon inflammation by IL-10 secretion.7 On the other hand, Th2 cells mainly secreted IL-4 and its release in turn stimulated Th2 cell activation.22 As Treg-type cytokines IL-10, Th2-type cytokines IL-4 and IL-5 increased after B. adolescentis treatment in DSS model in our previous data, we subsequently attempted to identify the CD4+ T cell subtypes responsible for regulating colitis pathogenesis by B. adolescentis. Here, IL5 is linked to colitis.